Crystalline defenders: Silver nanoparticles as a new front in antimicrobial warfare

Abstract

The field of nanotechnology is capturing the attention of more and more researchers in their scholarly investigations. The presence of biologically active compounds in medicinal plants makes them an excellent choice for the synthesis of nanoparticles. This paper details the formation of crystalline silver nanoparticles (AgNPs) using a simple and environmentally friendly green synthesis technique. The nanoparticles were synthesized using plant extract of Taxus wallichiana as the reducing agent. Various analytical methods, including X-Ray Diffraction (XRD), UV–Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM), were employed to investigate the size and structure of the synthesized particles. The as-synthesized AgNPs exhibited a prominent absorption peak at 425 nm. The FTIR spectrum of the AgNPs featured multiple spectral bands across the 300–4000 cm⁻¹ region. XRD analysis confirmed the successful formation of silver nanoparticles, with the synthesized sample exhibiting distinct diffraction peaks at 2θ values of 37.09°, 43.29°, 65.32°, and 76.40°. The biosynthesized AgNPs formed spherical aggregates at the nanoscale, with particle diameters ranging from approximately 60 to 80 nm as revealed by FESEM. They were found to be effective against a variety of fungal pathogens, such as Aspergillus niger, A. fumigatus, Fusarium oxysporum, and Penicillium expansum, as well as bacterial strains including Staphylococcus aureus, Escherichia coli, Proteus vulgaris, and Klebsiella pneumoniae. The nanoparticles demonstrated inhibition zones of varying diameters at different concentrations, with Nystatin and Kanamycin serving as positive controls for the fungal and bacterial species, respectively. The largest inhibition zone (18.42 ± 0.43 mm) was observed at the highest dose (0.4 mg/ml) for Penicillium expansum, while the smallest (10.18 ± 0.13 mm) was noted at the lowest dose (0.2 mg/ml) for Aspergillus niger. For bacteria, the highest dose (2.5 mg/ml) produced the largest inhibition zone (12.78 ± 0.17 mm) in Klebsiella pneumoniae, while the lowest dose (l.9 mg/ml) led to the smallest inhibition zone (8.85 ± 0.25 mm) in Proteus vulgaris. The study revealed that the synthesized nanoparticles showed greater inhibition against fungal species than against bacterial species. This study provides evidence that green-synthesized AgNPs from the leaf extract of Taxus wallichiana can be effective against a wide range of pathogen species.